The present invention relates to a heater for heating and reconstitution of wet food or beverage products, and more specifically, to a dispenser that includes such a heater.
Conventional dispensers of hot wet food products such as sauce, e.g., cheese and tomato sauce, have product storage tanks, commonly made of stainless steel, to hold the product and heating rods which heat the product in the storage tank. The wet product is commonly supplied in bags or packages, which are arranged in the tank and connected to a dispenser outlet.
These conventional hot dispensers suffer from a number of drawbacks. For instance, they require a lengthy cold start period during which the tank filled with unheated wet product must be heated. They also require a long recovery time when heated wet product is dispensed, if replenish with unheated wet product. If the product-holding bag is not replenished, it is necessary to regulate the temperature of the heating rods.
In connection with the re-thermalization or reheating of food products, it is further a serious drawback that the product quality tends to degrade over time when kept at a high temperature for prolonged period of time.
Furthermore, microbiological safety is a serious concern once the bag or package has been opened, and is then maintained at an elevated temperature.
In order to overcome the above drawbacks, some conventional food dispensers include on-demand heaters. These conventional on-demand dispensers only heat the product when requested. Conventional on-demand heating dispensers include electrical resistance heating blocks that are connected to the product supply passage; such a heater being of the type used in coffee machines. The heating block is a thermal energy storage device that heats the product as it passes through the heating block. This requires a constant supply of electrical power to heating block in order to maintain it at a certain temperature, thereby wasting electrical energy and losing thermal energy to the environment. In general, conventional on-demand heaters are inefficient, among other reasons, because they heat the product indirectly. Furthermore, heaters with heating blocks where the product is passed through the block are in general undesirable for the heating of wet food due to difficulties in cleaning the heating block. Hence, an increased risk of contamination exists. Furthermore, for heating of wet product comprising larger size particles, there is an increasing risk of blockage of the heating block.
Swiss Patent 679 722 describes an industrial device for the warming of liquids, in particular milk, which comprises at least one microwave generator, at least one liquid conduit and a rectangular wave-guide which is crossed by the liquid conduit disposed in intersection with the wave-guide. However, the device is not suitable for a dispensing machine which would provide heated food on demand. Moreover, in the device, the electromagnetic energy is fed from two longitudinally spaced apart locations of the wave-guide and enters the wave-guide in a direction situated at right angle with respect to the longitudinal direction along which the wave-guide mainly extends. Bouncing and multiple modes of the electromagnetic energy are created within the wave-guide which would cause problems to control the reflected microwaves and also a relatively poor heating efficiency for a satisfactory use in on-demand dispensing machine.
U.S. Pat. No. 2,585,970 relates to an apparatus for heating fluids in industrial conditions by means of ultra high-frequency dielectric heating in which a low section tube is passed into a relatively large chamber which is orthogonally fed by a microwave field. This solution is not suitable to be implemented in a public dispensing machine for heating a fluid product on-demand as multiple modes are created consequently to the fact that the energy is fed from the side of a large chamber which has a cross-section of about one-half wavelength in diameter. Multiple modes in such a large chamber would result in a lack of efficiency and in a relatively important loss of energy which would fail to rapidly heat food products circulating at a high flow rate such as it is requested in on-demand food dispensing machine. The large chamber would also be too cumbersome to fit in the restricted room usually left available in the dispensing machines.
Other methods and apparatuses for reheating food products by electromagnetic energy are known which would not be well adapted to heat liquid or viscous products circulating in a dispensing machine such U.S. Pat. No. 3,336,142 or U.S. Pat. No. 5,589,093.
Thus, there is a need for heating devices which overcome these drawbacks, and the present invention provides such devices.
In particular, there is a need to propose an efficient solution which can be easily implemented in dispenser systems for rapidly heating viscous or liquid food products at a desired warm temperature of consumption and at relatively high flow rate as it is generally required in the conditions of on-demand dispensing systems.
The present invention relates to a dispenser which utilizes a heating device that has superior performance compared to conventional tank and on-demand heaters.
This device prevents degradation of the product by holding the product at ambient temperature while heating on-demand. This extends the possibility of supplying a constant quality of the dispensed product.
The invention also provides a dispenser system that reduces the risk of microbiological contamination. In particular, that problem that may exist in the area where the product package or bag is connected to the dispenser.
The invention also proposes a novel system that includes a relatively simple and small heating device which can find its place in restricted space of any usual vending machine or sauce dispenser.
Accordingly, what the invention provides is a dispenser for dispensing a heated wet food or beverage comprising a housing configured and dimensioned for receiving the wet food or beverage, a heating device including an electrical power supply and a magnetron configured to supply electromagnetic energy in the microwave range to a wave-guide, and a heating passage configured to supply a wet food or beverage on-demand and arranged to intersect the wave-guide, to heat the wet food or beverage when electromagnetic energy is applied within the wave-guide, wherein the wave-guide has an elongated hollow shape and has an inlet for supplying the electromagnetic energy which is provided at a first end of the wave-guide so as to guide the electromagnetic energy substantially in forming standing waves along the longitudinal direction of the wave-guide while the other end of the wave-guide has a shorted end. Such a feeding configuration of the electromagnetic energy oriented in a longitudinal direction and also specifically in relation to the heating passage has proved to be particularly efficient to heat rapidly and efficiently with a minimum of energy loss a liquid food product circulating at relatively high flow rate in the heating passage. One important advantage of having a standing wave configuration is that we can tap the maximum power where the electromagnetic field is always at the maximum; i.e., at a predetermined distance along the wave-guide. The shorted end and its position allow setting up the correct predetermined distance while minimizing the reflected energy to the magnetron. More specifically, it has been determined that the preferable distance for the heating passage to intersect the longitudinal direction of the wave-guide and where maximum power is received is about 0.75 time of the wavelength as measured from the shorted end.
In another embodiment, the invention relates to a method of producing a heated wet food or beverage. This method comprises the steps of providing a dispenser of the type described herein, supplying a wet food or beverage to the housing, conveying the wet food or beverage from the housing to the heating passage, passing the wet food or beverage through the heating passage, while simultaneously applying electromagnetic energy in a standing wave configuration to a first end of wave-guide along a longitudinal direction of the wave-guide to thereby generate heat within the wet food or beverage, and then dispensing the heated wet food or beverage through the dispenser head.